Heat-treating system



Aug. 21, 1945. LE 2,383,203

HEAT TREATING SYSTEM Filed Dec. 9, 1941 5 Sheets-Sheet 2 Aug. 21, 1945.J M, LEE 2,383,203

HEAT TREATING SYSTEM Filed Dec. 9, 1941 5 Sheets-Sheet 3 E N jrzvmhvr.fmrlea. a: WW /My .flzbrlzqlst Aug. 21, 1945. J LEE 2,383,203

HEAT TREATING SYSTEM 7 Aug. 21, 1945. J LEE 2,383,203

HEAT TREATING SYSTEM Filed Dec. 9, 1941 5 Sheets-Sheet 5 r269 W269 35 7t -i i r f 1 l\ a\ n f LC r *am 282 gig; r290 r336 L337 25/ RAISE 05- A?1 7 Mercia) J warle Patented Aug. 21, 1945 UNITED STATES PATENT OFFICEHEAT-TREATING SYSTEM Jess Max Lee, Los Angeles, Calif.

Application December 9, 1941, Serial No. 422,214

4 Claims.

My invention has reference to heat treating systems of a type whereinmetals are sequentially heated and quenched. The objects and purposes ofmy invention will appear from what follows.

In its present typical and preferred form my invention has beendeveloped specifically with a view to heat treatment of aluminum alloys,such as are extensively used in aircraft construction. The inventionwill be typically and illustratively described particularly as appliedto the treatment of such alloys; but the invention is not necessarilylimited thereto.

Past experience and practice in the heat treatment of aluminum alloysindicates that best results, including maximum resistance to corrosionand best grain structure and strength, are obtained when the alloy iscompletely quenched within a period of five seconds removal from thehigh temperature zone. The alloy (in the form of sheets, shapes, etc.)is first heated to a temperature of around 950 F. to 1050 F. (dependingon the alloy) and maintained at that temperature for a length of timewhich depends upon the thickness or mass of the piece or pieces, and isthen quenched quickly. The quenching operation is usually performed byremoving the parts from the heat treating furnace or oven and quicklyimmersing them in water. Practice indicates that, for best results, notmore than approximately five seconds should intervene between removalfrom the furnace and final attainment of a specified low temperature.(The Army and Navy respectively specify that the quenching water shallbe kept below temperatures of 150 F. and 100' F.; that is, that thetemperature of the alloy articles shall be brought to approximatelythose maximum water temperatures within the quenching period.) Thequenching operation thus necessarily requires rather fast movement ofthe alloy articles.

At the high temperatures to which the alloy is initially heated, themetals are comparatively soft and have little physical strength.Particularly in the treatment of thin sheets and plates, the impactforces generated by fast immersion in the body of water is very likelyto warp and distort the articles; and that distortion is very dimcult toremove satisfactorily after the articles have been quenched: in somecases impossible.

It is one of the general purposes of my invention to provide a heattreating system and apparatus in which metal articles of any size, shapeand mass may be expeditiously removed from the heating furnace andquickly immersed and quenched, and complete cooling attained within theindicated time limits, with the minimum amount of. distortion.

One of the primary objects of the invention is to carry out the completequenching operation in a very short period; and that objective entailsthe objects of attaining fast movement of the load of metal from thefurnace into the quenching bath, and of rapid heat transfer in the bath;And in connection with those objectives it is also a general object toprovide an apparatus and a method wherein the sequences of operationscan easily be standardized, and wherein a certain amount of automaticcontrol makes standardization comparatively easy of attainment. It isconsequently one of my general objec s, and a correspondingaccomplishment of the invention, that the system is easily capable ofstandardized operation.

Other general objectives of the invention are the provision of apparatuswhich is relatively simple and compact, occupies a minimum floor space,and has low maintenance requirements. All these and further purposes andobjects will be best understood from the following descriptions.

The features of the system and apparatus which accomplish these purposeswill be best understood from the following detailed and specificdescription of an illustrative form of the invention. I may howeverpreliminarily mention that, among other features which will appear, myinvention is characterized by provisions for fast removalof the load ofmetal from the furnace and movement into the body of quenching water orother fluid with a slowing down of movement at the point of entry: andalso characterized by the application of water spray to the load for ashort period just prior to entry into the body of water. Theseprovisions give the metal greater strength and rigidity by the time itenters the water body, materially reduce the forces generated by waterimpact, and enable the complete quenching of the metal within theindicated time limit with minimum distortion.

In connection with the following illustrative description I refer to theaccompanying drawings in which:

Fig. 1 is a vertical central section of the complete apparatus, withcertain parts shown in elevation, the sections and elevations bein asindicated by line ll on Fig. 2. This figure shows the load-carryingelevator in its floor level position;

Fig. 2 is an enlarged fragmentary section taken as indicated by line2--2 on Fig. 1, but with the load-carrying elevator in its lowermostposition;

Fig. 3 is an enlarged view partly in vertical section and partly inelevation, the elevation being taken as indicated by line 3-4 on Fig. 2and the section as indicated by line 30-31: on Fig. 2. In this figurethe load carrying elevator is in uppermost position with the load in thefurnace;

Fig. 4 is an enlarged horizontal plan of lower parts of the apparatus,taken as indicated by line 4-4 on Fig. 1;

Fig. 5 is an enlarged detail elevation and section taken as indicated online 55 of Fig. 4

Fig. 6 is an enlarged horizontal sectlon on line 66 of Fig. 5; butshowing the traveler I13, I as if in a position below line 6-4;

Fig. '7 is a diagrammatic section taken as indicated by line on Fig. 6;

Fig. 8 is a diagram of the-electrical parts of the operating andcontrolling system;

Fig. 9 is an enlarged detail section taken as indicated by line 9-9 onFig. 4 with the elevator locked in its uppermost position as shown inFigs. 3 and 4.

The furnace or oven chamber designated generally by the numeral issupported on a suitable supporting structure which includes columns 2|and horizontal beams 22. Incorporated in the structure of the furnaceand its support are two horizontal door supporting rails (channels orsimilar structural members) 23 which extend along lower oppositeexterior edges of the furnace structure and act as supports and guidingrails for the two horizontally movable doors 24 which close theotherwise open lower end of the furnace chamber. In Fig. 1 the sectionis taken in a vertical plane which lies longitudinally of the movementof the doors. In that figure the doors are shown closed, meeting eachother at their inner edges at 24a, and their opening movements areoutwardly in the direction indicated by the arrows. The two doors arehung at each of their ends on rails 23 through the medium of rollerhangers 26. Their inner edge faces 24a which meet when the doors areclosed,.are provided each with a plurality of registering semi-cylindricnotches 24b which accommodate certain load supporting columns of theelevator when the elevator is supporting the load within the furnace andthe doors are closed. The mechanism for moving the doors will, bedescribed presently, after I first give a brief description of thefurnace structure.

The furnace structure proper is made with side walls 30, end walls 3|and roof 32, of suitable heat insulating and heat refractory material.Spaced inside the side walls I provide partitions 33, en-

closing spaces 34 for heated air circulation and for. the installationof electrical heating elements where such are used. For clarity ofillustration the electrical heating elements are not illustrated in Fig.l but are illustrated at 65 in Fig. 3.

Mounted directly under the furnace roof is a metal box-like structurewhich provides circulation ducts for the air and also provides fordistribution of the heated air over and throughout the load in thefurnace. 'This box-like structure has an upper wall 40 into the centerof which the air duct 4| opens from the circulation blower 42. Thebox-like structure has lower walls or panels 43 and longitudinalpartitions 44 which enclose two longitudinal air ducts 45. These ducts45 are in communication with air channels 34 through the openings at 46.Openings 46 are controlled by dampers 41, adjustable through the mediumof damper rods 48. Blower 42 takes air from ducts 45 through an airintake 49 which has openings communicating with ducts 45. (The smalllocalized section within the break line indicated A in Fig. 2 shows acommunication of 49 with 45. The dotted lines labeled 49 in Fig. 3indicate the positions of the communication openings.)

The lower wall 43 of the box-like structure, between the twolongitudinal partitions 44, is open except for the adjustable louvers50. These louvers, preferably of sheet metal and of the sectional shapesindicated in Fig. 2, extend transversely across the opening in thebottom of the box-like structure and are adiustably slidablelongitudinally of the furnace in guides 5| which support their ends.They are arranged in overlapping pairs; and the pairs may be slidablyad- Justed so that adjusted gaps are left between the pairs todistribute the heated air which is circulated downwardly by blower 42.By adjusting the louvers the hot air can be directed and distributed soas to obtain even heating and even temperatures throughout any load.Thermocouples may be distributed in the furnace and the load tofacilitate the obtaining of even tempera- I the heated-air at anyselected temperature.

As will be understood from what has been said, the circulation of airtakes place upwardly through passages 34 over heated elements 35,thence.

through ducts 45 and the intake 49 to the blower 42, thence downwardlyfrom the blower through 4| and distributively through the adjustedlouvers. The heated air flowing downwardly from the louvers isdistributed evenly upon and through the load, and thence the air passesagain to the bottom of channel 34 through openings "a near the loweredge of partitions 32.

The load of metal which is being heat treated is representeddiagrammatically at L. The load is usually carried upon a suitable truck(not specifically illustrated) and the diagrammatic shewing at L merelyillustrates the space which the load and the truck may occupy. Thewheels of such a truck are indicated in Fig. 3 at 60. The truckscommonly have three or more pairs of such wheels, symmetrically spacedlengthwise under the truck. And the elevator platform whichl willsubsequently describe is, among other things, especially designed tocarry such a multi-wheeled truck. In the subsequent detailed descriptionof the elevator I specifically describe a platform designed for a sixwheeled truck; but that is intended to be typical of any multi-wheeledarrangement.

I revert now to the mechanism for moving the doors 24. Fig. 3 shows, infull lines, the closed position of the doors as does also Fig. 1. Fig. 1shows the positions of the parts when the loaded truck is standing atthe floor level F and the doors are closed. This is the position of theparts either just before the load is lifted into the furnace chamber, orjust after the load has moved out of the furnace chamber to the floorlevel. Fig. 3, in full lines, shows the positions of the parts when theload is in the furnace chamber.

and the doors are closed.

At one end of falls 23 there is a transverse shaft which carries at eachend a sprocket 66.. (Only one of these sprockets is shown; but the doormoving arrangement at the other end of shaft 65 is the same as shown inFig. 2 and 'now described.) A sprocket chain 61 is trained over eachsprocket 66. One end of each chain is secured at 68 to a of eachsprocket chain 61 has a rod extension III which is attached at H to abracket 12 mounted on the other door 24.

At the other ends of rails 23 there are two sprockets H mounted on crossshaft I; and over each of these sprockets a chain I6 is turned, one endof each chain being secured at II to a bracket 18 mounted upon the righthand door, and the other end of the chain, extended by rod I9, beingconnected at 80' with a bracket 8| mounted on the left hand door. Thearrangement is such that rotation of shaft 65 will cause equal andopposite translation of the two doors, keeping them at all timesparallel to themselves.

The power medium which is applied to move the doors may be any suitablemedium. But, for reasons which will hereinafter appear, I prefer toutilize compressed air for operating the elevator of my system, andconsequently find it preferable to also utilize compressed air foroperating the doors. Accordingly I show a door operating cylinder 85 andpiston 86. Piston rod 81 is connected with the gear rack 88 which mesheswith a gear 89 on shaft 65, so that vertical movement of piston 86 willrotate shaft 65 to move the doors in and out. The cylinder is suitablysupported in any manner, shown as supported on a framework 90 mounted onone of the rails23. In the arrangement as shown, downward movement ofpiston 86 opens the doors to the positions indicated in dotted lines inFig. 3, while upward piston movement closes the doors to their full linepositions. Operation of the piston is controlled by inlet and exhaustvalves arranged in pairs. Fig. 3 is not intended to illustrate theactual physical arrangement of the valves, but illustrates the valve andpiping connections diagrammatically merely for clarity of illustration.Thus, I show diagrammatically a pipe 9I connecting into the upper end ofthe cylinder and having two branches, an inlet pipe 92 and an exhaustpipe 93. Inlet pipe 92 is controlled by a valve I94 which will behereinafter referred to as the upper inlet valve. Exhaust pipe 93 iscontrolled by a valve E-94 which will be referred to as the upperexhaust valve. Another pipe 95 connects into the lower end of cylinder85 and its inlet and exhaust branches 98 and 91 are controlledrespectively by the lower inlet valve I-98 and the lower exhaust valveE--98. The two inlet pipes 92 and 96 are diagrammatically shown asjoining a common pressure supply pipe 99 which leads from any suitablesource of air pressure, conveniently the common source from which airpressure is obtained for operating the other parts of the completeapparatus. The four valves (as are all the other control valves whichare referred to hereinafter) are assumed to be of a type normally closedby a spring and opened only when electrical energy is supplied to theirsolenoids I00. Operation of the doors to open or close, as may be, iseffected by supplying electrical energy simultaneously to the upperinlet valve 1-94 and the lower exhaust valve E98, or simultaneously tothe upper exhaust valve E94 and the lower inlet valve E-98.

A four pole single throw switch i-4 is mounted on one of the rails 23 ina suitable position to be operated by an operating lug IIII mounted onone of the doors when the doors are in or approaching their openpositions. This switch i-a' is of a type which is normally open andwhich is closed by engagement of lug IUI with its. operating arm I02.This occurs when lug IIlI moves to the left in Fig. 3. Lug IIII movesunder switch arm I02 and throws it to its dotted line position just asdoor 24 reaches its open position. Fig. 8 indicates how the switch willbe closed when such movement occurs. As will later appear, this is oneof the controlling switches of the control system. Another switch 21,single throw double pole, and of a type normally open, is mounted insuch a position as to be actuated to closed position by the lug IIIIwhen the door 24 has moved to the right to its closed position. Thecontrol functions of these two switches will be explained later. Switch9 is of the sa e physical type as switch -d; see Figs. 3 and 8.

Furnace chamber 20 is supported on columns 2| at a sufficient heightabove floor'line F to accommodate the truck and load L, supported at thefloor line, with reasonable clearance under doors 24. The relativepositions are shown in Fig. 1. In this position the truck with its loadmay be rolled off the floor onto the elevator, and vice versa.

A quenching pit III] is formed in any suitable manner below the floorline and centrally under furnace chamber 20. The depth of this pit maybe varied; it is only necessary that-the pit be deep enough to contain abody of quenching fluid deep enough to completely submerge the load whenit is lowered to the bottom of the pit and of sufllcient volume to haveno excessive temperature rise when quenching a maximum load. The pit maybe made larger or deeper for the purpose of accommodating a larger bodyof quenching fluid if that is found desirable in order to keep themaximum fluid temperature below the prescribed limit. On the other hand,as will be well understood, fluid may be constantly flowed through thepit in order to keep the temperature from rising above the limit. In thedrawings water is shown in thepit to the level indicated W. L. in Fig.2.

- I will commonly refer to water as the quenching fluid but withoutintending to limit myself to its use. In the variety of uses of which mysystem is capable, various quenching fluids may be used. Thus, for heattreating different metals the quenching fluid may be either water, oroil or other liquids, or even cooled gases, such as refrigerated air.And what I here say about the quenching bath is also true of the coolingsprays subsequently described; the spray fluid may be whatever liquid orgas best suits the particular operation being carried on, although therealso I refer to use of water as typical.

Extending downwardly from the bottom of pit I I 0 I provide a verticalelevator cylinder I I I. The walls H2 of the pit may typically be ofconcrete and the bottom of the pit may be formed with a floor recess I I3 to accommodate the packing gland Ill and to form shoulders H5 on whichthe elevator carriage may rest when fully lowered. Through and below thelowermost parts of the concrete work a downward casing H6 may beextended, with the elevator cylinder III contained within it. Elevatorplunger II! has a shouldered head H8 on its lower end which preferablyengages with cylinder head sleeve I I9 to form a positive stop to theupward movement of the elevator plunger and of the elevator as a whole,thus to position the elevator carriage and platform and the loadaccurately within furnace chamber 20.

Use of a vertical elevator of the hydraulic ram type, in and below thequenching pit directly under the furnace, is one of the features of mysystem which greatly simplifies the structur and operation of theapparatus and. conserves floor space.

Fig. 1 shows an air pipe I50 which extends down 7 dinal beam zontallyextending plate I21 whose vertical width from the floor level and enterscylinder III at its upper end. The valves for controlling the flow ofair through this pipe are not shown in Fig. l but are diagrammaticallyshown in Fig. 4. Fig. 4 is not intended to show the actual physicalplacement of the valves, but. only their functional relation to air pipeI50. In the actual apparatus these valves, as well as the valves whichcontrol operations of doors 24, may be mounted in some suitable remotelocation, as on a valve panel.

As shown diagrammatically in Fig. 4 two intake valves I--I 5I and I-I 52are connected in parallel relation between air pipe I50 and air supplypipe Valve I-I5I has a relatively large aperture and will be referred toas the large inlet valve, while valve I-I52 has a relatively smallaperture and will be referred to as the small inlet valve. Alsoconnected to air pipe I50, in parallel relationship, are a large exhaustvalve E-I 5I and a small exhaust valve E-I52. The speed at which airunder pressure is introduced into the elevator cylinder, or exhaustedfrom it, depends upon whether the large or the small inlet or exhaustvalves are opened, or both the large and small. Further, the main airpressure supply pipe may be provided with a manually settable valve I55and the exhaust pipe I56 may be equipped with a similar manual valve I51so that the speed of elevator operation may be, additionally, regulatedin a general way by the setting of these valves. The valves are all ofthe same type as here'nbefore described; that is, they are normallyspring closed and are opened when supplied with suitable electricalenergy.

..accumulate in the lower end of the cylinder by condensation orotherwise. It may also be used for introducing and maintaining anypredetermined amount of liquid, such as oilor water or both, in thelower end of the cylinder so as to effectively vary the air capacity ofthe cylinder. As will appear afterwards, I may wish to controllablyadjust the elastic compression and expansion characteristcs of the airin the cylinder, so as to adjust the length and the time period of thevibratory stroke which the piston may go through when supported by theelastic body of air under certain conditions. When the elevator islowered toward its bottom position both exhaust valves are normallyopen. Shortly before the bottom is reached, the large exhaust valve isclosed. The momentum of the elevator compressrrs the remaining body ofair inthe cylinder, and the elevator bounces. In bouncing itqnay reopenand then again close the large exhaust valve; but in any case it bouncesuntil the water in the quenching pit clamps the elevator movement anduntil the slow release of air through the small exhaust valve lets itsettle down to bottom position.

An elevator carriage frame I25, best shown in Figs. 2, 3 and 4 ismounted upon the upper end of elevator plunger III. This framepreferably includes a single longitudinal beam I26 which is centrallymounted on the upper end of plunger 1. At each end of longitu- I26 thereis a transverse horiis equal to the height of beam I26. Diagonal bracesI28 are secured to beam I26, and their outer ends are secured to spacerblocks I29 which are also secured to the outer ends of plates I21. Allof the parts so far described may be welded or otherwise suitablysecured together. Guide rollers I30 are mounted on pins I3I supportedbetween the spaced ends of plates I21 and braces I28. These guiderollers may be of any suitable and known form; for instance they may bein the form of interconnected gears and the vertical rails I35 may haveracks with which the gears mesh to prevent the elevator carriage fromtipping when unsymmetrically loaded. The carriage frame also carriesoperating pins I32 and I320 for certain controlling switches which aremounted on two of the four vertical rails I35 which form guides for thecarriage rollers. Of these switches, the one which is hereinafteridentified as b-c is mounted on one of the vertical rails I35 to beactuated by pin I32; and the ones hereinafter identified as d and k aremounted on another vertical rail to be actuated by the pin I32a. Thenatures and functions of these switches will be hereinafter described.

The vertical guide rails I35 extend from the shoulder H5 at the bottomof the well upwardly to a level just under doors 24. The lower portionsof the rails may be anchored to the walls of the well in any suitablemanner, and their upper portions braced by such braces as indicated atI36.

At or near their upper ends, the rails I35 carry apertured locking lugsI31 which form one element of a locking means for positively locking theelevator in the uppermost position shown in Fig. 3. At a lower levelrails I35 have another set of similar apertured locking lugs I3Ia whichform one element or means for positively locking the elevator with itsplatform or rack at th floor level, in the position shown in Fig. 1.These latter locking lugs are somewhatlbelow the floor level at thelevel of theelevator carriage frame in Fig. 1.

Slida'ble lockingbolt I40 are mounted in guiding brackets I on each ofthe end plates I21 and are extended and retracted b manual rotation ofpivoted arms I42 mounted on a shaft I43 which extends the length of thecarriage rame so that both pivoted a ms I42 may be simu taneouslyrotated. Links I44 connect arms I42 with bolts I 40. At one end of shaftI 43 another similar arm I45 (or a disk) is mounted, and this arm hassockets I46 adapted to receive a 'bar for the manual rotation of shaftI43. By mani ulation of the parts. it will be read ly understood howlocking b'olts I40 mav be projected i to the apertured locking lugs I31or I3'Ia or retracted from them. The socketed part I45 is somewhat belowthe floor line when the elevator is locked in the position of Fig. 1 atthe floor level, but t e sockets may readily be reached with an operatinbar. Alternatively. any suitable known mean of remote operation may beappl ed to the lockin bolts.

Automatic means are later described for keening the elevator and itsload su ported by adequate air pressure at all times, and forautomatically maintaining the elevator and load in their properuppermost positions when the load is in the-furnace in the position ofFig. 3. The positive locking means are provided as safety devices tohold the elevator and load in either of the two described positions incase there should be fa lure of the operating air pressure. and al o tohold the elevator rigid at the fioor level position while loads arebeing transferred to and from the ele vator. It is desirable that thearrangement be such that the positive locking means cannot be releasedunless the elevator and load are adequately supported by the fluidpressure, in order to preclude the possibility of uncontrolled descentof the elevator and load. Ordinarily, the frictional engagement oflocking bars I40 with looking lugs I31 under the downward pressure ofthe unsupported elevator and load will be suflicient to either make itimpossible for the locking bars to be manually retracted, or at least tomake that retraction ufficiently difllcult to give the operator adefinite indication that the elevator and load are not fully supportedby the air pressure. This action may be enhanced 'by providing rough orcorrugated surfaces of engagement between the locking bars and lockinglugs; or it may be made positive by providing small notches a in thelower edges of locking bars I40, the notches being adapted to hook overthe lower edges I31b of the apertures in locking lugs I3'1 if theelevator and load are not fully supported by the fluid pressure. SeeFig. 9.

For purposes which will appear, I do not mount the load-carrying truckdirectly upon the elevator carriage frame, but upon a platform which isremovably mounted upon that carriage frame in such a manner that theplatform is the only part of the elevator structure to be subjected tothe furnace heat, and so that the platform may be easily removed andreplaced in case it should deteriorate under the heat. The preferredform of structure is shown in the drawings. The platform includes twolongitudinal rail beams I60, preferably composed of channel irons andsupported on three spaced pairs of transverse supporting plates or barsI6I and I62. I show three, to accommodate a truck with three pairs ofwheels; the number of course will vary, three are to be taken only astypical. All of these pairs of bars are welded at their centers to theupper ends of tubes I63 which telescopically fit down over threevertical posts I64 which are mounted and secured at their lower ends, asby welding, to the central longitudinal beam I26 of the carriage frame.Cap disks I65 are welded to the upper ends of tubes I63 and rest on theupper ends of posts I64 to carry the load thrust. The outer ends of thecentral bar pair I62 are welded as indicated at I66 to the rail beamsI60. The outer ends of the other two pairs-of supporting bars I6I merelyextend under the rail beams I60 but are not welded to them. Thisarrangement allows longitudinal expansion and contraction of rails I60without warping the structure. The longitudinal spacings of the pairs ofsupporting bars I 6I, I62, are such that the wheels 60 of theloadcarrying truck, when on rails I60, will come directly over thetransverse supporting bars. The load weight is thus not carried on railsI60 at points intermediate the rail supports, and thus the structure isprotected against distortion which might otherwise be due to the weightforces when the platform is at'elevated temperature.

When the elevator and load are in the position shown in Fig. 3 and thedoors closed, the door edge notches 24b accommodate the columnarsupports of the elevator platform. In this position the platform has asubstantial vertical clearance abovethe doors and the carriage I25 hasclearance below the doors. The platform clearance over the doors issomewhat more than the amount of elevator movement required to actuatethe automatic controls which keep the elevator fully supported in itsuppermost position. That control is described later.

With the load in the furnace, the only part of the elevator that is inthe furnace is the platform. All other elevator parts are outside thefurnace where they are not subject to heat deterioration. The platformitself is of small mass; consequently little heat is wasted in heatingthe elevator-the no pay" load in the furnace is a minimum.

I have described how certain of the elevator control switches aremounted on vertical guide rails I35 at or near their upper ends. Theseswitches are the ones which, in the control system, control the elevatormovements at or near the upper end of its travel, and for that reasonare preferably mounted on the guide rails. Other switches which are nowto be described and which control the lower movements of the elevatorare not conveniently mountable upon the guide rails as theywould thus beclose to or under the water level in the pit. For such reasons avertical switch-carrying panel I10 is provided adjacent one of thevertical guide rails I35 (the guide rail shown at the upper left in Fig.4) The body of this panel is made up of two channel-shaped members I",and longitudinal T-beams I 12. Within the. space between members I1 I,and guided by them, is a vertically movable traveler I13 which carriestwo protruding switch actuating pins I14 and which has a cable sheaveI16 mounted upon it. A cable I16 is secured at one end at I11 to theupper part of the switch panel and extends down and under sheave I15 andthen upwardly to pass over a sheave I18 and thence over another sheaveI19 and thence downwardly, as shown at I16a in Fig. 5 to be secured tosome part of the elevator carriage frame. Fig. 4 shows how the end ofthe cable may be secured, at "61) to the switch actuating pin I32a whichis carried on the carriage frame. Sheaves I18 and I19 may be mounted ona brace plate I00 which is secured to the upper end. of guide rail I35and to the upper end of the switch panel. The whole arrangement is suchthat traveler I13 and its switch actuating pins I14 move verticallyalong the switch panel through distances equal to one-half the elevatortravel. The switch panel may thus be materially shorter than the lengthof the elevator travel; the lower end of the switch panel may beaccommodated in a well MI.

The two T-rails I12 form mounting rails for the various switches. Thestructure: of the whole switch panel may of course be varied widely butas shown in the drawings the two channel-shaped members "I are spacedlysecured together by rectangular frames I=B5 which surround and aresecured to members III at spaced levels. T-rails I12 are secured to theouter faces of the rectangular frames I so that the rails are somewhatspaced from member III, as shown in Fig. 6. Switch mounting clamps I86are mounted upon the rails in such a manner as is shown in Fig. 6 andare adjustable to any selected vertical position, and settable in theselected positions by tightening the clamps. These clamps carry bracketsI81 upon which the several switches are mounted, and the switches arethus very accurately adjustable as to their vertical positions. Typicalpositions f the switches are shown in Fig. 5.

The uppermost one of these switches, the one which is actuated when theelevator is nearest the bottom of its travel, is the switch labeled h.

vator travel, the next switch on the panel is the one labeled a, whichis actuated when the elevator is just a short distance below its floorline position-the elevator position shown in Fig. 1. This switch a is ofthe two-pole, double-throw, snap-over type, as indicateddiagrammatically in Fig. 8.

Next in downward order on the switch panel,

and upward order with reference to elevator,

travel, are the two switches which are labeled respectively a and c-e.These two switches are in eifect located substantially at the floorlevel. Switch a is a two-pole-single-circuit switch of a type which isnormally closed and which is temporarily opened by movement of itsswitch arm in either direction. The diagram of the switch in Fig. 8indicates its mode of operation. It is temporarily opened by theelevator movement at the floor level when one of the switch actuat ingpins I14 wipes by its roller m on its actuating arm I90 in eitherdirection. Figs. 6 and 7 show the typical relation of the pins I'll tothe switch arms, Fig. 7 showing typical relation of pin I14, travellingalong line Illa, to the actuating arms of switches a and 1.

Next in downward order on the switch panel and upward order on theelevator movement is a switch labeled 1. This switch is similar toswitch a and is located to be actuated by one of the actuating pins I14when the elevator is a short distance above the floor level.

The relationship of the several switch operating arms to the switchactuating pins I'll is shown in Fig. 6, which shows the two switches aand e-e'. Switch a is shown as having an operating arm I90 with apin-engaging roller I9I at its end. Switch H is shown as having a doubleoperating arm I92, I93. From Figs. 6 and 7 it will be readily understoodhow the arms and rollers protrude into the vertical travel path ofactuating pins I" so that the pins, by their up and down travel, eitherwipe by the actuating arms to temporarily actuate such a switch as a, orto snap the operating arm of such a switch as e-e' from one position tothe other. The arm structure of switch I is typical of all the switchesof snap-over type herein described.

Fig. 7, which is an enlarged section taken on line 1-1 of Fig. 6, showsthe relation of typical switches a and f to one of the switch operatingpins Ill. The pin travels along the dot-dash line I'Ila. Operating armI90 and roller IOI of the single throw switch a are shown in normal(switch closed) position. The dotted lines show the two positions towhich the arm is thrown to open the switch as pin I'll wipes by theroller in either direction. The double operating arm I92--l93 of thetypical snap-over switch I is shown in full lines in one of itspositions. It will be snapped over to the dotted line position by upwardtravel of pin I14 (downward travel of the elevator) and then back againto the full line position by downward travel of the pin.

Switches d, e-e', g, h, and k are all snap-over switches of the samegeneral physical nature as switch I and are operated in the same manner,either by one of the pins I14 on the switch panel or by one of the pinsI32, "2a on the elevator carriage. Some of these switches aredoublethrow, some single-throw, as shown in Fig. 8. Switch b--c (mountedat the top of a guide rail I35 and actuated by pin I32) is of a physicalnature similar to switches -4 and m. It is normally held in one positionto close the switch b, as indicated in Fig. 8; that is, it is normallyopen as regards the switch 0. Actuating pin I32 moves vertically pastroller lIlIb on the end of its operating arm I02a. The arm normallystands at such an angle (see Fig. 8) that pin I32 wiping by in eitherdirection will throw the switch blade temporarily to close switch c andopen I). As soon as pin I32 has passed the switch goes back to normalposition with 0 open and b closed.

Spray pipes 200 are shown in positions spaced around the space occupiedby load L when it is at floor level position as shown in Fig. 1. Theplacement and positions of the spray pipes as here shown are merelytypical; they may be placed and mounted in any manner around or over theload, so; as to thoroughly spray the load with cold water or othercooling fluid as the load moves down toward the water bath. An

electrically operated control valve 2M controls water supply to thespray distribution pipes 202. Switch 21 controls valve "I.

The general sequence of operations will now be explained, followed by anexplanation of the control system which effects the sequences.

At the start of a heat-treating sequence the elevator is at the floorlevel as shown in Fig. 1; preferably locked in position by the positivelocking bars I40, but also supportedby air pressure in the elevatorcylinder. A previously treated load has been removed with the elevatorin that position. A truck loaded with a fresh batch of metal to betreated is rolled onto the elevator platform and made fast in anysuitable manner. Locking bars I40 are then withdrawn, doors 24 areopened, and air pressure admitted to the elevator cylinder to move theelevator up until the elevator platform and the load are completelywithin the furnace chamber above the level of the doors. See Fig. 3. Thedoors are then closed, the load brought up to the required temperature,and maintained at that temperature for the desired length of time. Whenthe doors close they are moved into tight sealing engagement with thelower edges of the furnace walls. The door carrying rollers 26 roll upon small wedges 2641 as the doors reach closed positions, moving thedoors up against sealing gaskets 26!; (see Figs. 2 and 3).

While the load is in the furnace the elevator is supported in its upperposition by air pressure, preferably maintained automatically as will bedescribed. The elevator may also be positively locked in that position,as a safety measure to prevent the load weight from being imposed on thedoors in case the air pressure should fail for any reason. Also, in longcontinued heatings the air pressure and the automatic controls may beshut off if desired, for conservation of energy. In any case, however,the elevator cannot be unlocked (or at least readily unlocked) forlowering unless the air pressure fully supports it and the load.

When high temperature treatment is completed the elevator is unlockedand the doors opened -'Air pressure is then exhausted from the elevatorcylinder to lower the load. As soon as the load clears the doors theyare again closed. The doors are normally kept closed to conserve furnaceheat, only being opened temporarily for passage of the load in and out.In the present design door closure occurs as the lowering elevator nearits floor level position (Fig. 1). The clearance of the load under thedoors at floor level position may be made to be as large as desired,although it is preferred to keep it restricted so as to minimize thedistance that the load has to travel between the furnace and the waterbath and so as to minimize the necessary speed of that travel;

As the load approaches the floor level position and just before enteringthe water bath, its speed is momentarily checked and the sprays areturned on. The exact sequence of those two operations is notsignificant. It is desirable that the load be sprayed, before enteringthe water, sufficiently to sharply lower its tem'perature and increasethe strength of the metal before striking the water. But it is preferredto close the doors before starting the water spray, to prevent sprayentering the furnace. Checking the speed of the load just beforeentering the water has the effect of decreasing the impact forces but ofcourse lengthens the time period elapsing between load emergence fromthe furnace and entry into the water. While some pre-entry hesitation ofthe load may be had without preventing full quenching of the load withinthe prescribed time limit solely in the water bath, the preliminaryspraying is advantageous because it starts the quenching operationimmediately after emergence from the furnace and thus not onlystrengthens the metal to withstand the water impact but also facilitatesthe travel hesitation becausethe time required inthe water bath tocomplete quenching is thus reduced. The preliminary cooling caused bysprayin also facilitates the maintenance of the water bath at anyrequired low temperature, less heat having to be absorbed by the bath.

As hereinafter explained, the spraying continues until the load issubmerged. The hesitation in travel takes place just before load entryinto the bath, and after the load strikes the water at reduced speed itthen moves on downward at what would be full speed except for the waterresistance. Near the bottom of the elevator travel the downward speed isagain checked by closing the larger one of the elevator-cylinder exhaustvalves. Momentum of the elevator and load causes the load to bounce onthe air cushion in the elevator cylinder, and in bouncing it mayrepeatedly open and close the large exhaust valve,

' until release of the pressure through the smaller exhaust valve letsthe elevator gradually settle to the bottom on the floor shoulders I I5.The bouncing action agitates the water bath and promotes fast heattransfer to the water.

proper vertical locations with relation to elevator travel; Figs. 2 and5 show the relative vertical locations of the switches. However Fig. 8shows each individual elevator-actuated switch in the verticalorientation it would assume if the switch were actuated directly by theelevator movement rather than by a member which moves oppositely to theelevator. And in the following part of the description, I refer toswitch movements as up" or down, having reference to the orientations ofFig. 8 and reference to movements of the switch blades. In Fig. 8switches of the snapover type (whether single or double throw) arediagrammatically shown with two operating arms, as for instance the twooperating arms I92, I93 shown for switch I. Switches of the type whichare normally closed or open in one position and are operated onlytemporarily to the other position are shown with a single operating armand roller, as arm I and roller I9I of switch a, or arm IBM and roller1% of switch bc, or the roller carrying arm I02 of switch i-y' or p.Fig. 8 shows all the switches in the positions assumed when the elevatoris resting on bottom.

Starting with the elevator on bottom, the operator moves the raisebutton 250 in the direc tion indicated by the arrow in Fig. 8 to closethe raising circuit which leads from power supply line 240 through 2,then through the automatic button 242 thence through 2431, 244, theraise button 250, and thence through 25I and 252 through the normallyclosed switch a, and thence through 253 and 254 through the actuatingcoil 255 of the small intake valve II52, and thence through 256 and 251to power lead 258. At this time switch It is closed to close a parallelcircuit 259, 260, 26I to energize solenoid 262 of the large intake valveI-I5I. The elevator then moves upwardly and during this upward movementit first closes switch h (which is located say about 24" from the bottomof the elevator travel) and then, just before the elevator reaches itsfloor level position (Fig. 1) it throws switch 9 to a position oppositeto that shown in Fig. 8. Those two switches are in the lowering controlcircuit which is only operative when either one of -the lowering buttonsare closed. The effect of actuation of these two switches during upwardtravel of the elevator is merely to leave them both in their positionseffective for the subsequent lowering operation of the elevator.

Next, as the elevator moves upwardly, switch a is actuated to open it ator about the floor level position of the elevator. Opening of switch abreaks the described raising circuit, deenergizing both the intakevalves, and the elevator comes to a stop at its floor level position,with switch a still held open. Switch a is located in such a position,and

the physical engagement of operating pin I14 with its operating rollerI9I is of sufficient vertical extent to allow the elevator to come to astop before switch a is allowed to close again. In this position theelevator may be physically locked and the loaded truck run on to it.

The loaded elevator cannot now be moved further upwardly until furnacedoors 24 are opened. When these doors are fully opened they close theswitch i7'. Switch 2 parallels switch a by reason of the connections215, 216. Closing switch at thus again completes the raising circuit.

The furnace doors are normally closed as the elevator moves upwardlyinto its floor level position. To open the doors the operator closes theopen button 265 which closes the door opening circuit which leads frompower leads 240 through 266, the open button, and through 261, 268,switch b, 269, and thence in parallel through winding 210 of lowerexhaust valve E-98, and winding 2H 01' upper intake valve 1-94, andthence through 212 to the other power lead 258. As a result, piston 86of the door operating mechanism is moved downwardly to open the doors.

At the end of the door opening movement,

8 assaaoa switch actuating lug I] (see Fig. 3) engages the roller onoperating arm I02 of switch i-ivto close that switch and hold it closedas long as the doors remain open. Switch i is in parallel with switch a,by connections 21! and 218, so that the closing of switch 1 again closesthe raising circuit of raisingj button 250, which was broken by theopening ofswitch a. Consequently the subsequent closure of the raisingbutton again energizes both the large and small intake valves I-lll and1-452 of the elevator to introduce air under pressure to the elevator tocause further upward movement.

In passing, it should be noted that about the same time that switch a isopened by the elevator arriving at the floor level, or at least at atime before the elevator moves its load up between the furnace doors,the switch e--e' is thrown to a position opposite to that shown in Fig.8 (down, in that figure). The general function of switch e has to dowith the automatic lowering operation of the elevator, which will bedescribed later. The general function of switch e is to prevent closingof the furnace doors at any time while the load is between the doors.The action of these switches, as well as of switch d will presently bedescribed. The switch e-e' is located on the switch panel I10 (see Fig.at substantially what corresponds to the floor level position of theelevator.

As the elevator moves up from the floor level position, switch I, whichis located on switch panel H0 in eifect just above the elevator floorlevel position, is thrown down to a position opposite to that shown inFig. 8. This switch, like switch It and g, has only to do with thelowering operations.

As the elevator proceeds on upwardly, and at a distance of say about 12inches from its uppermost position, switch It (mounted on one of theguide rails I35, see Fig. 5) is snapped down to a position opposite tothat shown in Fig. 8, and thus opened. Switch it controls the individualcircuit of winding 262 of the large intake valve 1-! 5|. The largeintake valve thus closes as the elevator approaches its uppermostposition, leaving only the small intake valve Il52 open, and theelevator slows down.

Finally, as the elevator reaches or approaches closely to the top of itsmovement, switch d (also located on one of the guide rails l85see Fig.5) is snapped over to a position opposite to that shown in Fig. 8. Aswill be explained, switch d has to do with the door closing circuit, andits movement to the last stated position enables the door closingcircuit to be operated. That circuit was broken when switch e' wasthrown down at the floor level position, and is now re-made by switch (1being thrown down.

Also, at about the same time that switch (I is snapped over, and just asthe elevator approaches its final uppermost position, the switch 17-0 istransiently operated to throw'it'to position opposite to that shown inFig. 8 as the actuating pin I32 wipes past it. In the uppermost elevatorposition the pin has passed above the rollers I02b on switch arm IBM.The switch b-c is of the type which has a normal spring actuatedposition which is shown in Fig. 8. If the elevator moves down a shortdistance, its operating pin I32 moves down into operative re-engagementwith the arm roller of the switch and again opens switch b and closesswitch 0. The function of this switch, as later explained, is toautomatically feed air under pressure into the elevator cylinder to keepthe elevator supported in its uppermost position.

The door-closing circuits and functions of switches e-e' and d will nowbe explained.

The circuit which eifects and controls the closing operation of thedoors is as follows: "Close" button 280 is connected at one side by 28Ito a contact 282 which is connected through raise" button 250 withcontact 288 when the raise button is in normal position-open as regardsthe previously described raising circuit. The last named contact 288 isconnected by 284 to 243 which is connected through the automatic" buttonand 2" with power lead 240. (The purpose of this circuiting of the"close" and the raise" button is to make them inetl'ective whenever theautomatic" lowering button is used to lower the elevator.) The otherside of close switch 280 is connected by 288 and 288 with one of theupper pair of contacts of switch d, and by 281 with one of the lowerpair of contacts of that switch. The other upper contact isconnected by288 with one of the upper pair of contacts of switch e; and the otherlower contact of switch 11 is connected by 288 with one of the lowerpair of contacts of switch e. The other upper contact of e and the otherlower contact of that switch are both connected by 280, Ml with both theenergizing coils 292 and 283 of the upper exhaust valve E-Ol and thelower inlet valve I88 of the door operating mechanism, the two co vbeingconnected in parallel between 298 and 21 which leads to the other powerlead 258. The circuiting arrangement is such that the described doorclosing circuit cannot be energized unless the switches e' and d areboth in their upper or both in their lower positions. With the twoswitch blades in relatively opposite positions no circuit can beestablished because 288 is in circuit only when both switches are up and288 in circuit only when both switches are down. As has been stated,switch c has been snapped down when the elevator passed its floor levelposition, while switch d was still up. Thus, until switch d is throwndown when the elevator reaches its uppermost position, the door closingcircuit cannot be closed to energize valve coils 292, 293 to operate thedoor mechanism to close the doors. But as soon as the elevator, in orclose to its uppermost position, snaps switch d down then the doors canbe closed.

As stated before, the elevator is stopped mechanically at the upper endof its travel by engagement of plunger shoulder I I8 with the lower endof sleeve 9. The operator keeps raise button 282 closeduntil theelevator reaches its upper position, and then, or any time just before,closes the door close button 280 until the doors close. The elevator maythen be mechanically locked in its upper position for safety.

Switch b-c is a two-pole double throw switch normally held in its upperposition (in Fig. 8) by its spring. In that position it puts the openingbutton 265 in circuit to be effective to open the furnace doors. As theswitch operating pin I32 (see Fig. 4) moves up with the elevatorapproaching uppermost position, the lug wipes by roller I02b of theswitch, momentarily reversing it but allowing it to move again to normalposition (Fig. 8) when the elevator reaches top position. The doors areat this time open, so the temporary breaking of the opening circuit atswitch b is of no effect. The temporary closing of switch 0 is neitherof any effect because its two contacts are connected by 300 and 30! inparallel with the raising button 250 which is at this time supposed ofswitch closes the previously described to be closed. (Ifthe operatorshould release the raising button 200 just before the elevator reachesthe top, the closed switch c, in parallel with the raising button, willcause the elevator to move on to its uppermost position.) However, afterthe raising buttonis opened then if the elevator sinks by reasons of airleakage, the operating pin I32 wipes down onto switch roller I 02b andagain throws the switch down (Fig. 8). This occurs before the elevatorhas sunk far enough to let the elevator platform contact the doors.Closing raising circuit to feed air to the elevator to raise it untilthe switch is allowed to go back to normal position (Fig. 8). Theelevator and its load are thus automatically kept at uppermost positionif the elevator is not mechanically locked. And if it is mechanicallylocked, the elevator is constantly fully supported by the air pressureso that it will not drop when unlocked. And while switch b is open(whenever the elevator has sunk) the door opening circuitcontrolled bythat switch cannot be closed to open the doors. This provision makescertain that the doors cannot be opened when there is any liability ofthe elevator load being upon them.

When the elevator and load are to be lowered,

it is first necessary to open the furnace doors and mechanically unlockthe elevator. For reasons which have been stated, neither of theseoperations can be performed unless the elevator and load are fullysupported in their upper positions. And, as will be seen, in one of themodes of control operation the elevator cannot .be then lowered untilthe furnace doors are fully opened.

when the furnace doors are opened, switch i-a is thrown to closedposition and held there until the doors subsequently start their closingmovement. The function of'switch i in conjunction with switch a has beenexplained. Switch i when closed energizes a relay to close certain relayswitches which have control functions in the circuits whichcontrol theautomatic lowering operation of the e1evator--an operation in which thelowering necessarily automatically 2' back to its upper position.

follows door opening. In manual operation of the system the doors areopened as previously explained. In that mode of operation the elevatormust remain in its upper position in order to open the doors due to thecontrol of switch b on the door opening circuit; but manual control isdepended on to not start the lowering of the elevator until the doorsare fully open.

Manually controlled lowering of the elevator is controlled by either orboth the lowering buttons 305 and 306. from lead 240 through 301 to thebutton, thence through 308 and 309 to and through the set of switches fand g, and thence through 310, coil 3 of the large exhaust valve E-l5l,and 3I2, switch h and M3, 26| and 251 to the other lead 258. Thelowering button 305 thus controls the large exhaust valve E-l5l, subjectto the controls of switches f, g and h. Switch 71. is always closedexcept when the elevator is near the, bottom of its travel. Switches 1and g were left in their position opposite to that of Fig. 8 (snappeddown) when the elevator passed the floor line position on its previousmovement up. The circuit through I and g at the time now underconsideration is as follows: from 309 through the lower contacts ofswitch f, thence through 3| 5, the lower contacts of switch g to 3l0.

The circuit for lowering button 306 is from lead 240 through 320, thebutton, thence through The circuit for button 305 is 32L winding 322 ofsmall exhaust valve i l-I52, and thence through 323, 26] and 251 to theother lead 258. The small exhaust valve will remain open as long aslowering button 306 is held closed, being subject to no other manualcontrol.

If lowering button 305 is closed the large exhaust valve E-l5l opens andthe elevator moves down until switch I is snapped over (up in Fig. 8)lust above the floor line position. Switch .f now being in its upperposition, the circuit through I and g is broken and the elevator maystop before it reaches switch g at a position just below the floor line.However if at this time, or previously, the operator has closed button306 to open small exhaust valve El52, the elevator will proceed ondownwardly, butat slowed pace until it reaches switch g to snap it overto its upper position (Fig. 8). The circuit to the large exhaust valveis then re-established through switches f and g as follows: from 309through 325, the upper contacts of switch I, then through 326, the uppercontacts of switch g, and 321 to 3|0. The opening of the large exhaustvalve beins to accelerate the elevator in its downward motion at justabout the time the loaded truck L enters the water. The loadconsequently strikes the water at low speed, but is increasinglyaccelerated as it enters, so that the load is quickly submerged andquenched. The relative degree of retard, or hesitation of movement, asthe load approaches the water depends on several factors, such as thedistance between the two switches f and g and the sizes of the twoexhaust valves, all of which may be adjustably changed.

Just as the elevator starts down switch d is reversed to its upperposition in Fig. 8. With switch e still in its lower position the doorclosing circuit is broken, making it impossible to close the furnacedoors until the elevator reaches the floor level position where itreverses switch The doors may then be closed by closing the button 200either at that time or previously. The door closing circuit is then thesame'as before stated except that it extends through the switches d ande as follows: from 285, through 286, upper contacts of switch d, 208,uppercontacts of switch e, to 290. V

Incidentally, switch 0 is momentarily closed immediately after theelevator starts down and has the momentary effect of energizing theraising control circuit. But at that time switch It is open and disablesthe large intake valve I-I5l, so that the closing of 0 only opens thesmall intake valve I-|52. The large exhaust valve E-I5l, if not bothexhaust valves, being open, the elevator continues down. Shortlyafterwards the switch is is thrown back to its closed position.

Also incidentally the switch a is momentarily opened as the elevatorpasses the floor level position, but its opening is ineffective as thecircuit of the raising button 250 is open at that time. Switch afunctions only to stop the elevator at the floor level on its way up.'

As the elevator approaches its bottom position switch 11. is againopened. breaking the circuit of the large exhaust valve El5l. Theclosure of that valve, at about two feet above bottom, produces thebounce and agitation before explained. The elevator then settles to thebottom with the small exhaust valve open. The generator then releasesthe lowering button or buttons. The parts of the control circuit arethen all in the positions initially described and shown in Fig. 8. Thenext operation is to raise the quenched load as previously described.

In Fig. 8 the energizingcoil 338 of spray valve 21H is shown asconnected across leads 240 and 258, by connectors 282 and 333, in serieswith spray button 831. In lowering the elevator under manual control,the operator applies the spray during the slow travel of the heatedload, before and as the load enters the water bath. Automatic operationof the spray will be explained after the automatic lowering operationhas been described.

The electrically controlled operations when the automatic button 242 isused for lowering the elevator will now be described. At the beginningof these operations the elevator is in uppermost position and the doorsare closed. The several switches are in the same positions beforedescribed; the positions to which they are thrown by the upward travelof the elevator to its.

248. In the operated or closed position of, automatic button 242 thesecircuits are broken,

so that the manual closing button and raising button cannot be usedsimultaneously with the automatic button.

When the automatic button is closed, circuit is established from lead248 through 2, 835, the button, 338, the two lower contacts of switch e(which is then down), 821, 288, switch b (which must be closed tocomplete the circuit) 288, door operating valve coils 218 and 2H, and212 to the lead 258. The doors then open, provided the elevator is clearup and switch I) is closed. The door operating valves remain open untiltheir circuit is broken when switch e is thrown up as the elevatorpasses the floor level.

When the doors are fully open. switch {-4 closes and establishes acircuit from button 242 through 348, switch :I, I", relay magnet 342,and 343 to 251 and lead 258. The relay switches m, n and 0, close. Relayswitch m closes a selfholding circuit 344 (between 3 and 848) inparallel with switch i to hold the relay closed after switch i opens andas long as the automatic button 242 is held closed. (It is held closeduntil the elevator reaches bottom.)

Switch 1: closes a circuit 2, button. 242, 848, switch n, 345, toconductor 32l, in parallel with the manual lowering button 388. Closureof switch n (with 242 closed) consequently opens the small exhaust valveE-l52 by the same gkrcuit control as has been explained for buttonSwitch 0 closes a circuit from lead 248 through 24!, button 242, 848,switch 0, 348 to conductor 389 leading to switches j and g: this circuitbeing in parallel with lowering button 885. Closure of switch 0 (withbutton 242 closed) consequently closes the energizing circuits of thelarge exhaust valve E-ISI in the same manner that lowering button 385closes them; that is, subject to the described controls of switches f, gand h. These switches, operate as before described; the elevator goesthrough the same hesitation as described, and switch h and the bounce"near the bottom are operated in the same manner. After the elevatorsettles to the bottom the automatic button is released and all theswitches are then again in the positions of Fig. 8.

During the downward movement before reaching the floor level switches H,d and k are operated in the same manner as in the manual operation andwith the same eflects. At the floor level switch e-e is snapped over toits upper position (Fig. 8) as before described; but it now has theautomatic function of causing door closure without closing button 288being manually operated.

When the automatic button 242 is originally closed it establishesthecircuit through "8, switch e (then down in Fig. 8), I31, and switch b(then down) to open the furnace doors. This has been described. Thiscircuit is finally broken when switch e-e' is thrown to its upperposition at the floor level position of the elevator; and then switch eautomatically establishes a door closing circuit as follows. With button242 closed the circuit goes from 838, through 358, the upper contacts ofswitch e, SM, 288, the upper contacts of switch d (then up), 288, uppercontacts of switch e, 290, the coils 282, 288 of the valves which effectdoor closure, and thence through 212 to lead 258. In this operation theautomatic switch e acts in these circuits in parallel with the' manualclosing button 280 and thus effects the same functions as that button,but automatically.

Automatic operation of the spraying system is such as to begin sprayingat about the time the load approaches or reaches the floor level, and tocontinue spraying until the load is submerged. As the doors closesubstantially at the time desired for spray inception, and because itmay be undesirable to start the spray until the doors are closed ornearly closed, I may control the spray in the manner now described.

Switch 1), of the same mechanical type as switch i-i, is mounted in sucha position on the frame of furnace as to be closed by. the switchoperating lug illl mounted on door 24, when the doors close. This switchis held closed only as long as the doors are closed and'opens as theybegin to open. p

In Fig. 8, switch p is shown in a circuit which leads from lead 258through 332, coil I88, I83, switch p, relay switch m, 340, button 242,and 335, 24!, to lead 240. With the automatic button 242 closed tooperate the doors and lower the elevator, relay switch m is closed whenthe doors are fully opened. The elevator then starts down, as described,and the doors then automatically close. As they close, the circuitthrough switch p is closed, switch m remaining closed as long as button242 is closed. Spraying then starts and continues to be applied to theload until it is completely submerged. The spray thus operates in ageneral way coincidently with the slow travel of the load. After theload submerges, the spray is of course ineffective; but in theillustrated control system it is finally shut off when button242 isreleased and relay switch m opens.

Many changes and variations may be made in the described apparatus andmethods, within the scope of my invention as defined in the followingclaims. In the claims as well as in the description I use the term bathwithout any limitation to requirement of a solid body of fluid; it maybe as well a heavy spray or shower. In other words the bath in which theheated load is submerged may be either a bath of solid. fluid or may bea spray or shower bath.

I claim:

1. In systems for heat treating metal articles and the like by firstheating and then quenching them, and which comprise a heating furnacehaving a closure at its lower side and means for opening and closing theclosure. 8. quenching bath spaced below the furnace, and an articlecarrying elevator mechanism adapted to move articles vertically into andbetween the furnace and when the doors are closed, the iimer ends ofsaid doors having openings for receiving the columnar supporting meanswhen the doors are nace, so that the carriage frame below the doors isnot subjected to the furnace heat.

v 2. In systems for heat treatingmetalv articles and the like by firstheating and then quenching them, and which" comprise a heating furnacehaving a closure at its lower side and means for,

opening and closing the closure, a quenching bath ,20 closed and theplatform is moved into the furdoors are closed, and the inner ends ofsaid doors having openings for receiving the-columnar supporting memberwhen the doors are closed and thplatform is moved into the furnace, sothat the carriage frame below the doors is: not sub- :Iected to thefurnace heat.

3. Systems for heat treating metal articles and the like as specified inclaim 1, further characterized by theload receiving platform beingskeletal and comprising a, plurality of longitudinally spaced transversebeams, the columnar supporting means. comprising a columnar supportarranged centrally under and supporting each beam. anda pair oftransversely spaced longitudinal rails mounted on the outer ends of. thetransvers beams, the rails adapted to take .a load carrying truck whosesupporting wheels may be positioned over the several transverse beams]4. Systems for heat treating metal articles and the like as specified inclaim 1, further characterized by the carriage frame comprising ahorizon- -tal longitudinal beam'mounted centrallyon the spaced below thefurnace, and an article carry,-

ing elevator mechanism adapted to move articles vertically into andbetween the furnace and bathp the improvement which comprises anelevator having a lower fluid pressure cylinder located below thequenching bath, a lift plunger extending upwardlyfrom the cylinderthrough the bath, an elevator carriage frame mounted on the upper end ofthe plunger, a centrally arranged columnar supporting member extendingupwardly from the carriage frame, a load receiving'platform, meansremovably mounting the platform nally spaced central columnarsupportsone' for I I each platformbeam on the carriage beam, the

upper end of the elevator plunger, the platform being .skeletalandcomprising a plurality of Iongitudinally spaced'transverse beams in B,horizontal"planespaced above the carriage beam with their transversecenters directly above that beam, and a pair or transversely spacedlongitudinal truck receiving rails mounted on the outer ends of thetransverse platform beams, and the columnar'supportin'g means comprisinglongitudiplatform' beams and rails being removable as v a 'unit from thecarriage frame."

on: the columnar supporting member vertically spaced abovev the carriageframe,, the. furnace closure comprising oppositely moving doors ar; 1, v

, ranged to have their inner ends meet-when the ".LMAx LEE.

